Popular smoking articles, such as cigarettes, may have a substantially cylindrical rod shaped structure and include a charge, roll or column of smokeable material such as shredded tobacco (e.g., in cut filler form) surrounded by a paper wrapper. Also, tobacco may be used for smokeless products such as chewing tobacco and other smokeless tobacco products. For example, various types of smokeless tobacco products are set forth in U.S. Patent Publication No. 2011/0048434 the disclosure of which is incorporated by reference herein in its entirety.
Throughout the years, various methods have been developed to improve the flavor of tobacco and tobacco products. In addition to improving flavor, it would be helpful to produce tobacco plants, and tobacco products derived from such plants, having reduced amounts of certain potentially toxic chemicals. For example, it would be of interest to produce tobacco plants and tobacco products having reduced heavy metals.
Cadmium (Cd) is a heavy metal that can be found in soils. In the field, phosphate fertilizers can be a source of cadmium and the concentration can vary based on agricultural practices, soil characteristics, climate and plant varieties (Lugon-Moulin et al., Agronomy for Sustainable Development, 26:151-156, 2006). Cadmium can accumulate in tobacco. Studies indicate that stalk position, crop year and growing region may have an effect on cadmium content. Also, due to differing climates and soils, establishment of true genetic differences in existing cultivars may be difficult to characterize with precision (Lugon-Moulin et al., Chemosphere, 63: 1074-1086, 2006). For example, studies indicate that potential cadmium accumulation differences may exist between the Nicotiana species but less so within varieties of Nicotiana tabacum (Wagner and Yeargan, Plant Physiology, 82: 274-279, 1986).
Since tobacco (e.g., lamina, stems, flowers and roots) is used in the manufacturing of cigarettes and alternative tobacco products, developing new cultivars that less effectively translocate heavy metals such as cadmium from roots to shoots may be beneficial.
Also, as tobacco can take up such environmental contaminants, tobacco lines that take up an increased amount of such compounds may be used to decrease the amount of such chemicals in soil (e.g., for soil clean-up).
Thus, there is a general need for methods that can provide plant lines comprising altered uptake of a heavy metal contaminant or other non-natural chemicals, or other compounds from the environment, where such compounds may be potentially toxic if ingested over long periods of time. The method should be designed so that even for plant species such as tobacco that have a complex genome and thus require screening of a large number of mutation events to isolate the mutation of interest, and that are large and thus require extensive facilities for breeding, screening for the desired phenotype is economical.